Dynamic Colors
In GeoGebra, you can change the objects' colour using the Colour tab of the
Properties Dialog.
The colour of an object can also be set to change dynamically: open the
Properties Dialog of the object whose colour you
would like to define, then select the Advanced tab. The Dynamic Colours sections contains three input boxes which
allow you to enter the main colour’s components: Red, Green, and Blue.
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Create three sliders a, b, and c with an interval from 0 to 1.
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Create a polygon, whose colour will be dynamically related to the sliders values.
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Open the
Properties Dialog for the polygon, then enter the names of the three sliders into the Red, Green and Blue input boxes.
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Close the
Properties Dialog and change the values of the sliders in order to find out how each colour component influences the resulting colour of the polygon.
You may also animate the sliders with different speeds, in order to see the colour of the polygon change automatically.
The Dynamic Colours section also contains an input box which allows you to change the Opacity of the selected object. You can enter a number ranging in [0,1] (where 0 means transparent, and 1 means 100% opaque), as well as a slider, in order to obtain a dynamic opacity. Other numbers will be ignored.
RGB / HSV / HSL
Some dynamic colouring patterns can be obtained using a different colour model. Besides the default
RGB, GeoGebra offers two more models, HSV
and HSL, that can be selected in the drop down list displayed at the bottom of
the Dynamic Colours section of the Advanced tab of the
Properties Dialog.
To make a point A go through all the colours of the rainbow when moved left and right, switch to HSV mode, then set
Saturation and Value to 1, and Hue to x(A)
.